1. Field of the Invention
The present invention relates to a method for producing a cordierite ceramic honeycomb structure by extruding.
2. Description of Related Art
Cordierite ceramic honeycomb structures are used as an exhaust gas purifying catalyst carrier, a filter, or a heat exchanger for automobiles or the industrial use.
Conventionally, a production method of a cordierite ceramic substrate disclosed in Japanese Patent Application Laid-Open No. 51-5313 mentions that the firing process can be conducted economically without generating a crack while maintaining characteristics necessary for a honeycomb substrate by reducing the amount of unprocessed clay (raw clay) included in the clay component in the material batch and replacing the same by processed clay (calcined clay) in preparing clay, talc and alumina materials for producing a honeycomb substrate having a cordierite phase as the main component.
Further, Japanese Patent Application Laid-Open No. 56-145171 discloses a technology for producing a cordierite body having the excellent thermal impact resistance, capable of conducting the firing process at a comparatively low temperature by using halloysite as the kaolin mineral and plate-like talc particles as the talc.
However, recently, a thinner wall and a higher cell density are desired particularly for a honeycomb carrier of a ceramic honeycomb catalyst carrier to be used for an exhaust gas apparatus for automobiles in order to improve the purifying performance according to the progress of the industrial technology.
In general, a cordierite ceramic honeycomb structure is produced by extruding in order to improve the mass productivity.
Therefore, in order to have a thinner wall and a higher cell density in the honeycomb carrier, it is important to improve the formability at the time of extruding.
In consideration of the point, the method of replacing the raw clay by the calcined clay disclosed in Japanese Patent Application Laid-Open No. 51-5313 remarkably deteriorates the formability at the time of extruding although the method is effective for reducing crack generation at the time of firing. Further, the method using halloysite disclosed in Japanese Patent Application Laid-Open No. 56-145171 can improve only the thermal impact resistance but the improvement in the formability in production cannot be expected.